A co-worker, Dave Dawson, sent me a picture of a grub that he found in his brother’s lawn while putting in a French drain.
The grub was buried about three or four inches into the soil. He thought it was amazing to see not one, but five or six grubs, while digging a trench about 2 feet long.
The life cycle of an annual white grub is considered a complete metamorphosis. It starts off as an egg, laid from May through July, depending on the species and location. The eggs hatch into larva or grubs and they feed on basically whatever is in front of their mouth. They will feed on soil, roots and other organic matter. After feeding for 6 to 8 weeks, they will dig themselves down into the soil to avoid the cold water.
Once it warms up again in the spring, they will rise just up into the root zone, continue feeding for a while, but not enough to cause any real damage to the growing grass. Then, the grubs will burrow down into the ground, pupate, and turn into an adult. The adult flies around for 4 to 6 weeks, laying eggs during the summer and then the whole process starts again.
We occasionally get lawn care service calls from customers in the spring saying they have grubs and want us to apply an insect control application. The feeding they do in the spring is very light, so they generally do not eat enough of the insect control product to be controlled. Plus, the grass is growing rapidly in the spring, so any roots that are eaten are quickly replaced.
The grubs Dave found were getting ready to pupate into adults. He did find one that was emerging from the pupal case as an adult as well, but before he could get a picture of it, his daughter decided to control it naturally, by squishing it with a rock.